MYSTERY: Female students gather at Sana'a University yesterday in Yemen, where a woman was arrested but later released as investigators focused on finding bomb maker Ibrahim Hassan al-Asiri and US-born cleric Anwar al-Awlaki. Photo: AP

Ibrahim Hassan al-Asiri who, (AP)

Imam Anwar al-Awlaki (AP)

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Authorities yesterday launched an international manhunt for the demonic al Qaeda explosives expert who has been identified as the No. 1 suspect in the potentially deadly mail-bomb attacks on the United States.

In addition to the mail-bomb plot, Saudi-born Ibrahim Hassan al-Asiri, 28, also is suspected in two previous terror attempts — packing the explosives for the Christmas “underwear bomber” aboard a flight to Detroit, and sending his own younger brother on a suicide mission, hiding a bomb in the young man’s body cavity, in a bid to assassinate Saudi Arabia’s intelligence chief.

“[This] is a very dangerous individual . . . And we need to find him,” Deputy National Security Adviser John Brennan told ABC.

Brennan said authorities are “looking at the potential” that the mail bombs — discovered Friday and addressed to synagogues in the Chicago area — were designed to blow up in mid-air.

“At this point, we, I think, would agree with the British that it looks as though they were designed to be detonated in flight,” Brennan told CBS, referring to the packages, one of which was intercepted on a UPS cargo plane outside of London, and the other on a FedEx jet in Dubai.

A Qatar Airways rep revealed that two passenger jets had been used to ferry the second mail bomb from Yemen to Dubai.

The clue that ties al-Asiri to the terror attempts was the particularly potent explosive used — pentaerythritol trinitrate, or PETN, authorities said.

The quantity used in the mail bombs was about five times the material stuffed in the underwear worn by Umar Farouk Abdulmutallab on the Detroit-bound plane, officials said.

Along with al-Asiri, authorities also are targeting another al Qaeda radical hiding in Yemen — American-born cleric Anwar al-Awlaki — in the bombings.

Saudi Arabia’s intelligence chief, Prince Mohammed bin Nayef — the person al-Asiri and his brother tried to kill — first tipped off the Americans about the mail bombs.

“It was a race against the clock to find those packages, to neutralize them,” Brennan said.

In fact, red-faced British officials yesterday admitted that they didn’t turn up their mail bomb during an initial, six-hour search of planes’ cargo after being alerted to the threat.

They discovered it only after retracing their steps and going back over packages, at the persistent urging of US authorities, a British source said.

One source called the bomb “the most sophisticated device ever found.”

Brennan said the mail-package explosives were designed to detonate on their own, without someone having to set them off.

“Only two have been found,” he told Fox News. “We cannot presume, though, that there are none others that are out there. And so we are looking at all the packages that originated in Yemen.”

Paul Nunziato, president of the Port Authority Police Benevolent Association, blasted his agency — which runs JFK, La Guardia and Newark airports — for what he called its “blatant lack of commitment to public safety” by not putting on extra patrols or K-9 units to inspect cargo in the wake of the mail-bomb plot. But PA spokesman John Kelly insisted, “Safety and security is a top priority for the Port Authority.

International authorities had suspected that a bomb might have been aboard the Boeing 747-400 operated by UPS that crashed in Dubai in September, killing two. But officials from the United Arab Emirates yesterday said no such device had been found.

Meanwhile, officials in Yemen released a 22-year-old co-ed who had been suspected of mailing the recent bombs.

They said they now believe that Hanan al Samawi, a fifth-year engineering student at Sana’a University who was busted Saturday, was the victim of identity theft.